Light diffusers are very widely used in lighting applications as one of the basic building blocks for luminaries. They are employed to diffuse light and, thus, to make light sources or luminaire exit windows give softer light.
With the current trend of using LED lights, and the glare associated with the small feature size of LEDs, there is particular attention devoted to optical diffusers.
In LED lighting applications, diffusers are applied to hide the LEDs, make the LEDs appear effectively larger or prevent an observer from looking directly into the LEDs. All these measures lead to decreased glare nuisance and better aesthetically looking luminaries.
The optical function of a diffuser is to scatter light and thus to produce softer light or more homogeneous light emitting surfaces (or exit windows). Light scattering is at the same time the main disadvantage of diffusers: they broaden the initial light beam giving an increase of the Etendue. This can be an undesirable consequence of the use of a diffuser.
This effect of light scattering by diffusers is shown in FIG. 1. Each light beam 10 that is incident on the diffuser 12 is broadened when generating the diffused output light 14. The broadening is proportional to the scattering strength of the diffuser. Therefore, in order to homogenize a certain light emitting surface by means of a diffuser, there is generally a need for additional beam-shaping optics to collimate the beam broadened by the diffuser.
It would therefore be desirable to provide a light diffuser which counteracts the problem of broadening the general output range of light directions, for example so that collimating optics for collimating the general output range of light directions can be avoided.
US20120037207 discloses an optical layer having opposing first and second main surfaces, wherein both the first and second surface comprise an array of angled facets with a respective angled orientation to its respective main surface.